Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $54.45   7.672%   $58.6274   $58.63   $58.65   $58.60  
  Purchase #2 $195.30   13.245%   $221.1675   $221.17   $221.15   $221.20  
  Purchase #3 $82.94   10.680%   $91.798   $91.80   $91.80   $91.80  
  Purchase #4 $175.31   10.612%   $193.9139   $193.91   $193.90   $193.90  
  Purchase #5 $113.52   12.729%   $127.97   $127.97   $127.95   $128.00  
  Purchase #6 $190.32   6.159%   $202.0418   $202.04   $202.05   $202.00  
  Purchase #7 $211.36   9.348%   $231.1179   $231.12   $231.10   $231.10  
  7 purchase totals = $1,023.20       $1,126.6365   $1,126.64   $1,126.60   $1,126.60